BUTTERMILK BASED COBALT PHTHALOCYANINE DISPERSED FERRICYANIDE MEDIATED AMPEROMETRIC BIOSENSOR FOR THE DETERMINATION OF XANTHINE

A tissue-based amperometric biosensor for xanthine determination has b een developed. The biosensor uses a carbon paste electrode (CPE) which contains buttermilk (BTM) as source of xanthine oxidase (XOD) (EC.1.1 .3.2.2.) and cobalt phthalocyanine (CoPc) as mediator. The system is a lso mediated with ferricyanide in solution to obtain a double-mediated biosensor. The effect of various variables upon the response was stud ied. Linearity was observed over the concentration range of 1-15 mM xa nthine. The optimum operational pH range for the electrode is 8.0-9.0. Reproducibility was studied and a relative standard deviation (rsd) o f 10.26 % was found. After 60 days the normalized response of the BTM- modified electrode was 60 % of the first day.